Molding materials reinforced with carbon fibers have been extensively utilized not only as structural materials for airplanes, motor vehicles, and the like but also in general industrial applications, sports applications, or the like, such as tennis rackets, golf club shafts, and fishing rods, so as to take advantage of the high specific strength and specific modulus thereof. Examples of the forms of carbon fibers for use in such applications include woven fabric produced from continuous fibers, UD sheet in which fibers are parallel arranged unidirectionally, random sheet produced from cut fibers, and nonwoven fabric.
In recent years, composites employing thermoplastic resins in place of the conventional thermosetting resins as the matrix are attracting attention. For example, a molding method has been developed in which a molding base composed of a mat made of discontinuous long fibers, and a thermoplastic resin impregnated thereinto is heated to a temperature not lower than the melting point of the thermoplastic resin and introduced into a mold regulated so as to have a temperature not higher than the melting point or glass transition temperature, and the mold is then clamped to thereby perform formation.
In the method of forming a fiber-reinforced molding material described in patent document 1, for example, a fiber-reinforced molding material having a size not smaller than the projected area of the mold is placed and the excessive portions are removed by the shear force applied during mold clamping, in order to simplify the steps for shaped-product production and improve the operation efficiency. Patent document 2 describes a molding method in which two sheets of molding material are press-molded to thereby obtain a shaped product in which the minimum thickness of a flange part is smaller than the thickness of the wall surface of the opening.
Meanwhile, patent document 3 employs a configuration in which a random mat used in a charge ratio that is small relative to the shape of the mold is press-molded to thereby avoid the occurrence of excessive portions.
Patent document 4 describes a technique in which a flange part is press-molded first and the remaining part is press-molded next.